Add render to turbo:before-stream-render event

Follow-up to hotwired#479 Related to hotwired/turbo-site#107 As an alternative to exposing an otherwise private and internal `StreamActions` "class", support custom `<turbo-stream action="...">` values the same way as custom `<turbo-frame>` rendering or `<body>` rendering: as part of its `turbo:before-render-stream` event. To change how Turbo renders the document during page rendering, client applications declare a `turbo:before-render` event listener that overrides its `CustomEvent.detail.render` function from its [default][PageRenderer.renderElement]. Similarly, to change how Turbo renders a frame, client applications declare a `turbo:before-frame-render` and override its `CustomEvent.detail.render` function from its [default][]. This commit introduces the `StreamElement.renderElement` function, and extends the existing `turbo:before-stream-render` event to support the same pattern with `StreamElement.renderElement` server as the default `CustomEvent.detail.render` value. With those changes in place, callers can declare a document-wide event listener and override based on the value of `StreamElement.action`: ```javascript const CustomActions = { customUpdate: (stream) => { /* ... */ } customReplace: (stream) => { /* ... */ } // ... } document.addEventListener("turbo:before-stream-render", (({ target, detail }) => { const defaultRender = detail.render detail.render = CustomActions[target.action] || defaultRender })) ``` [PageRenderer.renderElement]: https://github.com/hotwired/turbo/blob/256418fee0178ee483d82cd9bb579bd5df5a151f/src/core/drive/page_renderer.ts#L7-L13 [FrameRenderer.renderElement]: https://github.com/hotwired/turbo/blob/256418fee0178ee483d82cd9bb579bd5df5a151f/src/core/frames/frame_renderer.ts#L13-L24
seanpdoyle · Sep 12, 2022 · 7b3def6 · 7b3def6
1 parent 1c9ce3f
commit 7b3def6
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Showing 3 changed files with 30 additions and 8 deletions.
diff --git a/src/elements/stream_element.ts b/src/elements/stream_element.ts
@@ -1,7 +1,9 @@
 import { StreamActions } from "../core/streams/stream_actions"
 import { nextAnimationFrame } from "../util"
 
-export type TurboBeforeStreamRenderEvent = CustomEvent<{ newStream: StreamElement }>
+type Render = (currentElement: StreamElement) => Promise<void>
+
+export type TurboBeforeStreamRenderEvent = CustomEvent<{ newStream: StreamElement; render: Render }>
 
 // <turbo-stream action=replace target=id><template>...
 
@@ -26,6 +28,10 @@ export type TurboBeforeStreamRenderEvent = CustomEvent<{ newStream: StreamElemen
  *   </turbo-stream>
  */
 export class StreamElement extends HTMLElement {
+  static async renderElement(newElement: StreamElement): Promise<void> {
+    await newElement.performAction()
+  }
+
   async connectedCallback() {
     try {
       await this.render()
@@ -40,9 +46,11 @@ export class StreamElement extends HTMLElement {
 
   async render() {
     return (this.renderPromise ??= (async () => {
-      if (this.dispatchEvent(this.beforeRenderEvent)) {
+      const event = this.beforeRenderEvent
+
+      if (this.dispatchEvent(event)) {
         await nextAnimationFrame()
-        this.performAction()
+        await event.detail.render(this)
       }
     })())
   }
@@ -153,7 +161,7 @@ export class StreamElement extends HTMLElement {
     return new CustomEvent("turbo:before-stream-render", {
       bubbles: true,
       cancelable: true,
-      detail: { newStream: this },
+      detail: { newStream: this, render: StreamElement.renderElement },
     })
   }
 

diff --git a/src/tests/fixtures/stream.html b/src/tests/fixtures/stream.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html data-skip-event-details="turbo:submit-start turbo:submit-end">
   <head>
     <meta charset="utf-8">
     <title>Turbo Streams</title>
@@ -10,6 +10,7 @@
     <form id="append-target" method="post" action="/__turbo/messages">
       <input type="hidden" name="content" value="Hello world!">
       <input type="hidden" name="type" value="stream">
+      <input type="hidden" name="id" value="a-turbo-stream">
       <button>Create</button>
     </form>
 

diff --git a/src/tests/functional/stream_tests.ts b/src/tests/functional/stream_tests.ts
@@ -20,8 +20,11 @@ test("test receiving a stream message", async ({ page }) => {
 
 test("test dispatches a turbo:before-stream-render event", async ({ page }) => {
   await page.click("#append-target button")
-  const { newStream } = await nextEventNamed(page, "turbo:before-stream-render")
+  await nextEventNamed(page, "turbo:submit-end")
+  const [[type, { newStream }, target]] = await readEventLogs(page, 1)
 
+  assert.equal(type, "turbo:before-stream-render")
+  assert.equal(target, "a-turbo-stream")
   assert.ok(newStream.includes(`action="append"`))
   assert.ok(newStream.includes(`target="messages"`))
 })
@@ -73,9 +76,19 @@ test("test overriding with custom StreamActions", async ({ page }) => {
   const html = "Rendered with Custom Action"
 
   await page.evaluate((html) => {
-    window.Turbo.StreamActions.customUpdate = function () {
-      for (const target of this.targetElements) target.innerHTML = html
+    const CustomActions: Record<string, any> = {
+      customUpdate(newStream: { targetElements: HTMLElement[] }) {
+        for (const target of newStream.targetElements) target.innerHTML = html
+      },
     }
+
+    addEventListener("turbo:before-stream-render", (({ target, detail }: CustomEvent) => {
+      const stream = target as unknown as { action: string }
+
+      const defaultRender = detail.render
+      detail.render = CustomActions[stream.action] || defaultRender
+    }) as EventListener)
+
     window.Turbo.renderStreamMessage(`
       <turbo-stream action="customUpdate" target="messages">
         <template></template>